In recent years, in the field of WDM (Wavelength Division Multiplexing) networks, OADMs have been implemented (Optical Add Drop Multiplexers) and optical hubs, such as WXCs (Wavelength Cross Connects), that can split and insert traffic and can switch paths on a wavelength-by-wavelength basis without converting optical signals into electrical form.
The implementation of such equipment has made it possible to construct complicated networks, such as interconnected ring networks and mesh networks.
When designing a WDM network, optical network information, including information concerning stations where equipment constituting the WDM system can be placed and information concerning the optical fibers interconnecting the stations, is applied along with wavelength path information concerning wavelength paths propagating in the WDM network. Hereinafter, optical transmission equipment constituting such a WDM system may sometimes be referred to as “WDM equipment.” The WDM equipment includes, for example, equipment such as OADMs and ILAs (In-Line Amplifiers) or bypasses which are described later.
OADMs are placed at both end stations serving as the start and end points of a wavelength path, while on the other hand, at other stations serving as relay stations, ILAs or OADMs as repeaters can be placed. By using an OADM as a repeater, it is possible at each relay station to regenerate and relay any desired wavelength path and to compensate for a tilt of a WDM signal.
Rather than placing OADMs or ILAs, optical fibers may be simply connected at relay stations to relay optical signals. In the following description, any relay station where optical fibers are simply connected in this manner may sometimes be referred to as a “bypass station,” and the relay means constructed by simply connecting optical fibers may sometimes be referred to as a “bypass.”
An optical network design method is proposed which designs an optical network by using integer programming so that traffic flowing along a failed path is switched to another working optical path, thus eliminating the need to provide a dedicated protection optical path.
An optical network design method is also proposed which determines, by using integer programming, the placement of working and protection optical paths that minimizes the network cost in an optical network in which a plurality of optical transmission links share the same optical transmission equipment.